fix comments and docstrings misspelled words

Change-Id: I355b6fedf372b1273ceaebe22e8e890aa9c913c9
Closes-bug: #1267103
Fix typo in gridfs store

Closes-Bug: #1266986

Change-Id: Ic69ef987b785d0db25e2fea2a745f3d00780241a
replace type calls with isinstance

In store/__init__.py, there are two uses of the "type" method to
check type compatibility. It is better to use the "isinstance" method
since it will work for subtypes as well.

Change-Id: I20958aa449822cac2cb03e12557fded3f45a9e05
Closes-Bug: #1267074
Merge "replace type calls with isinstance"
Merge "fix comments and docstrings misspelled words"